NFL uses new metric to determine how contagious COVID-positive players are

HOUSTON, Texas (KTRK) -- In the NFL, there are numbers nearly everywhere, whether it's on jerseys, the scoreboard or down markers. But, in this age of COVID-19, there's one magic number: the cycle threshold.

The cycle threshold, called CT, is a metric used in PCR testing for COVID. Those tests, which tell us if a patient either tests positive or if the virus is undetected, feature rounds of analysis, or cycles, searching for the virus. The cycle threshold is a number which can indicate whether a person is still contagious. It's like keeping score in a football game. The higher number, the better.

Late in the season, the NFL pivoted on its policies. The league now views a CT value of 35 or greater as equal to a negative COVID test.

Therefore, vaccinated players who test positive for the virus can return to the team if they produce CT values of 35 or more, as the league does not view those players as contagious.

We asked Dr. Catherine Troisi, an infectious disease epidemiologist with UTHealth's School of Public Health, how reliable these CT values are.

"Lower cycle threshold, as you said, means more virus," Dr. Troisi noted. "But let's say it's 20 versus 40. What does that mean? Does it mean that the 20 isn't infectious? We don't really know. It's not perfect, but the NFL wants to get the players back on the field."

Since the number could tell us how contagious a person is, should the public be tested for CT values?

"Not all laboratories can report cycle threshold," Dr. Troisi said. "It would also add more time to getting the results, and if it's taking you three days to get your results anyways, you don't want to add on to that."
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